The present application relates to the field of extracting/depositing of fluid, and more particularly, to stirring/agitating of fluid to increase extraction of particles within the fluid and/or mixing of different fluids.
Extracting a sample fluid from a collection chamber of a fluidic system can be challenging, particularly when the collection chamber contains small amounts of fluid, such as in the range of approximately 1.5 milliliters to 10 microliters.
To extract fluid from a fluidic system such as a micro-well or micro-channel, a pipette is often used. If the fluid contains particles, such as organic or inorganic materials or biomaterials, the particles may become adhered to the container bottom or the container sidewalls. In these situations, the extracted fluid sample will have a reduced concentration of particles, this loss may compromise tests performed on the extracted fluid sample, comprising the limits of detection and producing increased false positives and ambiguity when the sample is analyzed. To increase the amount of particles extracted by a pipette, it is desirable to stir the fluid during the extraction process in order to disperse the particles from the channel walls and bottom, thereby increasing the likelihood that more particles are collected during the process. Adhesion of the particles may occur due to adhesive forces such as electrostatic or Van der Waals attractive forces.
Another use of fluidic systems is for mixing together two distinct fluids, for example, to obtain a chemical reaction, heat transfer, etc. Often the two fluids do not mix rapidly simply by bringing them together (i.e., only slow mixing occurs due to diffusion), resulting in a slow and incomplete mixing of the fluids. This result may affect the outcome of the process which may have been undertaken for commercial and/or experimental reasons. In each of the above situations and others, an active mixing of fluids may by desirable. Mixing may be useful when the fluid from the pipette is dispensed into a vial or a fluidic reservoir with another fluid. The mixing fluids may be used for an analysis or for an experiment.
One proposal for the agitation or stirring of fluids is by the use of a bead stirrer or external ultrasonic agitation. An alternative form of agitation is by fluid-flow induced agitation accomplished by pulsing the pipette, i.e., back and forth pumping of the liquid by application of an external pressure source. Examples of such ultrasonic and fluid-flow agitation are set forth in patents and applications cited within the Incorporation by Reference section of this document.